A computer network is a collection of interconnected computing devices that exchange data and share resources. In a packet-based network, such as the Internet, the computing devices communicate data by dividing the data into small blocks called packets. The packets are individually routed across the network from a source device to a destination device. The destination device extracts the data from the packets and assembles the data into its original form. Dividing the data into packets enables the source device to resend only those individual packets that may be lost during transmission.
In some instances, these packets may be directed to a single destination device in a type of communication referred to as a “unicast” communication. Many applications make use of unicast communications, such as web browsers that communicate via the HyperText Transfer Protocol (HTTP). Unicast communications (or “unicasting”), however, may not be appropriate for all applications, especially those that deliver substantially the same content at substantially the same time to a plurality of destination devices, such as Internet Protocol Television (IPTV), web-conferencing, video conferencing, and other multi-user applications. For these multi-user applications, the use of unicast communications would require delivery of the same content multiple times, i.e., a separate transmission for each destination device, which would unnecessarily consume network bandwidth and strain server resources. As a result, a form of communication referred to as “multicast” communication or “multicasting” was developed to address this unnecessary consumption of network resources.
Multicasting may involve using network devices to replicate data packets for receipt by multiple recipients and thereby reduce the transmission burden on the sender, leading to scalability and more efficient packet delivery. A sender of multicast communication transmits multicast packets to a single address, the multicast group address. Recipients may request to “join” the multicast group in accordance with a protocol, such as the Internet Group Management Protocol (IGMP). If the request is granted, packets sent to the group address are replicated by the network devices of the network and forwarded to the address of the joined recipient, along with all other previously joined recipients.
Multicast live-live techniques allow routers to use multicast techniques, such as join requests, to set up multiple redundant multicast streams across a network to improve robustness of content delivery in case of failures in the network. A receiving router receives multicast data packets on both a primary multicast forwarding path and a secondary multicast forwarding path. The receiving router forwards a primary one of the redundant multicast streams to the next-hop router, while dropping packets of a secondary one of the redundant multicast streams.